挤压态AZ31B镁合金动态拉压不对称性分析

Analysis on Asymmetry of Extruded AZ31B Magnesium Alloy between Dynamic Tension and Compression

为了研究挤压态AZ31B镁合金在高应变速率下的拉压不对称性,对挤压态AZ31B镁合金进行了织构分析。采用分离式Hopkinson压杆和反射式拉杆装置分别沿挤压方向和垂直挤压方向进行了动态压缩和拉伸试验,应变速率范围在500～2650s-1之间。结果表明,由于在挤压过程中形成了基面织构,沿挤压方向压缩时,拉伸孪晶{1012}<1120>容易启动,屈服强度对应变速率不敏感,且屈服强度较低;沿挤压方向拉伸时,拉伸孪晶不能启动,压缩孪晶{1011}<1120>和非基面滑移是其主要的塑性变形机制,合金屈服强度较高;合金在压缩和拉伸时表现出很强的拉压不对称性,压缩屈服强度与屈服强度的比值约为0.30。垂直于挤压方向拉伸和压缩时,没有表现出拉压不对称性。

In order to understand the asymmetry of extruded AZ31B magnesium alloy between dynamic tension and compression,texture analysis was performed,and dynamic compression and tension tests at extruded direction and transverse direction were carried out using a split Hopkinson pressure bar and a reflected hopkinson tension bar apparatus with average strain rates in the range of 500~2 650 s-1.The results show that due to the formation of basal plane texture during the extruding process,extension twins {1012}〈1120〉 are activated easily when the alloy is compressed along extruding direction,so yield stress is lower and insensitive to strain rates.When the alloy is tensioned along extruding direction,due to the tensile twins not be activated,contract twins {1011}〈1120〉 and non-basal slips are the main deformation mechanisms,leading to the higher yield stress of the alloy.The alloy shows a strong asymmetry between compression and tension,and the ratio of yield stress between compression and tension is about 0.30.Absence of asymmetry along transverse direction can be observed.